linux-kernel - Re: [BUG] kernel BUG at mm/vmacache.c:85!

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Date:	Tue, 29 Apr 2014 15:29:04 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Davidlohr Bueso <davidlohr@...com>,
	Hugh Dickins <hughd@...gle.com>, Linux MM <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rik van Riel <riel@...hat.com>,
	Michel Lespinasse <walken@...gle.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [BUG] kernel BUG at mm/vmacache.c:85!

On 04/29/2014 03:55 AM, Linus Torvalds wrote:
> On Mon, Apr 28, 2014 at 3:14 PM, Davidlohr Bueso <davidlohr@...com> wrote:
>>
>> I think that returning some stale/bogus vma is causing those segfaults
>> in udev. It shouldn't occur in a normal scenario. What puzzles me is
>> that it's not always reproducible. This makes me wonder what else is
>> going on...
> 
> I've replaced the BUG_ON() with a WARN_ON_ONCE(), and made it be
> unconditional (so you don't have to trigger the range check).
> 
> That might make it show up earlier and easier (and hopefully closer to
> the place that causes it). Maybe that makes it easier for Srivatsa to
> reproduce this. It doesn't make *my* machine do anything different,
> though.
> 
> Srivatsa? It's in current -git.
> 

I tried this, but still nothing so far. I rebooted 10-20 times, and also
tried multiple runs of multi-threaded ebizzy and kernel compilations,
but none of this hit the warning.

Is there anything more specific I can run to increase the chances of
hitting this? I guess a test-case might be too much to ask since I'm
the first one hitting this, but if anybody has suggestions of scenarios
which have a higher likelihood of hitting this (like running multi-
threaded workloads or whatever), I could probably give it a try as well.

Thank you!

Regards,
Srivatsa S. Bhat

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